Membrane receptors for very low density lipoprotein (VLDL) inhibitor of
lymphocyte proliferation
PI Yi, G Beck and S Zucker
Physiologic concentrations of human plasma very low density lipoproteins
inhibit the DNA synthesis of lymphocytes stimulated by allogeneic cells or
lectins. In this report we have compared the effects of isolated
lipoproteins [very low density lipoproteins (VLDL), low density
lipoproteins (LDL), and high density lipoproteins (HDL)] and
lipoprotein-depleted plasma (LDP) on DNA synthesis by
phytohemagglutinin-stimulated human lymphocytes. The relative potency for
the inhibition of lymphocyte proliferation was VLDL greater than LDL
greater than HDL greater than LDP. Fifty percent inhibition of DNA
synthesis was observed at a VLDL protein concentration of 1.5--2.0
microgram/ml. We have further demonstrated the presence of specific
receptors for VLDL on human lymphocytes. Native VLDL was more effective
than LDL in competing for 125I-VLDL binding sites. Subsequent to binding to
lymphocytes, 125I-VLDL was internalized and degraded to acid- soluble
products. Based on a Scatchard analysis of VLDL binding at 4 degrees C, the
number of VLDL receptors per lymphocyte was estimated at 28,000 +/- 1300.
Based on an estimated mean binding affinity for the VLDL receptor complex
at half saturation of approximately 8.8 X 10(7) liter/mole, it is estimated
that 91% of lymphocyte VLDL receptors are occupied at physiologic VLDL
concentrations in blood. Although the immune regulatory role of plasma
lipoproteins is uncertain, we suggest tha VLDL and LDL-In may maintain
circulating blood lymphocytes in a nonproliferative state via their
respective cell receptor mechanisms.
Volume 57,
Issue 6,
pp. 1055-1064,
06/01/1981
Copyright © 1981 by The American Society of Hematology
